In some code division multiple access (CDMA) wireless communication systems a radio link protocol (RLP) is employed in an attempt to achieve enhanced reliability in wireless communication. With RLP, if a new wirelessly transmitted frame is not received or is received but cannot be accurately decoded and/or interpreted, the receiving device may transmit a negative acknowledgement (NAK) to the device transmitting the frame after a subsequent frame is received correctly. Upon receipt of the NAK, the transmitting device retransmits the frame. Often, the transmitting device additionally increases transmit power when a NAK is received, and particularly if a predefined number of NAKs are received within a given period or based on a predefined amount of data transmitted.
In order to take full advantage of the NAK, the receiving device must be able to identify when a frame is missing and/or erased. As such, RLP protocol instructs that idle frames be periodically transmitted, such as at the end of a series of data-bearing frames. This allows the receiving device to accurately identify if a final data-bearing frame has not been received. For example, if a receiver receives a first frame (F1) with a first sequence number, a second frame (F2) with an incremented sequence number, and then an idle frame (I4) with a sequence number incremented twice, then the receiving device knows that the third frame (F3) was not received and can issue a NAK for the third frame (F3). Typically, about four to six idle frames are communicated after a series of data bearing frames are communicated (e.g., after a download or upload).
DCCH channels are additionally configured to provide for added capacity by taking advantage of the intermittent nature of speech and other communications by utilizing discontinuous transfer modes (DTX). With the use of DTXs, the transmitting device does not communicate during the periods of silence in speech and other periods of inactivity, instead a DTX is initiated. Because of the nature of DTX, prior receiving devices have been unable to distinguish between the DTX mode and erased frames. As such, previous receiving devices mistakenly identify DTXs as erased frames and requested an unnecessary increase in transmission power, resulting in increased transmission power and reduced capacity.
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